Gwihabaite is a rare ammonium potassium nitrate mineral (NH4,K)(NO3). It is orthorhombic in form, colorless with a vitreous luster. It has a Mohs hardness of 5 and a specific gravity of 1.77. It is deliquescent and water-soluble. The mineral is also known as nitrammite. It was first described in 1996 for an occurrence in Gcwihaba Caves (Drotsky's Cavern, type locality), Maun, North-West District, Botswana. The spelling of the name was simplified, omitting the "c", which represents the "click" sound used by the San people. It occurs as incrustations and efflorescences on cave surfaces formed by bacterial action on bat guano.[2][3]

Gwihabaite
General
CategoryMineral
Formula
(repeating unit)
(NH4,K)NO3
IMA symbolGwi[1]
Strunz classification5.NA.15
Dana classification18.01.03.01
Crystal systemOrthorhombic
Crystal classDipyramidal
Space groupPmna (No. 62)
Unit cella=7.075Å, b=7.647Å, c=5.779Å, Z=4
Identification
Formula mass85.31
ColourWhite, colourless
Crystal habitAcicular, Efflorescences
CleavageNone
Mohs scale hardness5
LusterVitreous
StreakWhite
DiaphaneityTransparent
Density1.77
Birefringence0.141
2V angle87◦
DispersionNone
SolubilitySoluble in H2O , deliquescent

References

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  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ Mineral Handbook
  3. ^ Mindat data